* {
	margin: 0;
	padding: 0;
	border: 0;
}
.login {
	z-index: 2;
	position: absolute;
	width: 350px;
	height: 500px;
	border-radius: 5px;	
	background: white;
	box-shadow: 0px 0px 5px #333333;
	top: 50%;
	left: 50%;
	margin-top: -250px;
	margin-left: -175px;
	transition: all 1s;
}
.logintext {
	font-size: 24px;
	margin-top: 100px;
	padding-left: 40px;
	box-sizing: border-box;
	color: #333333;
	margin-bottom: 50px;
}
.center {
	width: 100%;
	height: 30px;
	box-sizing: border-box;
	padding: 0 40px;
	margin-bottom: 30px;
}
.centerimg {
	width: 20px;
	height: 20px;
	float: left;
	margin-top: 5px;
}
.centerimg img {
	width: 20px;
	height: 20px;
}
.centerinput {
	float: left;
	height: 30px;
	width: 230px;
	margin-left: 15px;	
	position: relative;
}
.centerinput input {
	z-index: 2;
	transition: all 0.5s;
	padding-left: 10px;
	color: #333333;
	width: 100%;
	height: 30px;
	border-top: 1px solid #ffffff;
	border-left: 1px solid #ffffff;
	border-right: 1px solid #ffffff;
	border-bottom: 1px solid #cccccc;
	box-sizing: border-box;/*为元素设定的宽度和高度决定了元素的边框盒。
	为元素指定的任何内边距和边框都将在已设定的宽度和高度内进行绘制。*/
	outline:none;/*设置 4 个边框的样式*/
	position: relative;
}
.centerinput input:focus {
	border: 1px solid dodgerblue;
}
.inputtext1 {
	background: white;
	padding: 0 5px;
	position: absolute;
	z-index: 0;
	opacity: 0;
	height: 20px;
	top: 50%;
	margin-top: -10px;
	font-size: 14px;
	left: 5px;
	color: dodgerblue;
	line-height: 20px;
	transition: all 0.5s;	
}
.inputtext2 {
	background: white;
	padding: 0 5px;
	position: absolute;
	z-index: 0;
	opacity: 0;
	height: 20px;
	top: 50%;
	margin-top: -10px;
	font-size: 14px;
	left: 5px;
	color: dodgerblue;
	line-height: 20px;
	transition: all 0.5s;	
}
.inputtext3 {
	background: white;
	padding: 0 5px;
	position: absolute;
	z-index: 0;
	opacity: 0;
	height: 20px;
	top: 50%;
	margin-top: -10px;
	font-size: 14px;
	left: 5px;
	color: dodgerblue;
	line-height: 20px;
	transition: all 0.5s;	
}
/*选择获得焦点的输入框，设置其样式*/
input:focus ~.inputtext1 {
	top: 0;
	z-index: 3;
	opacity: 1;
	margin-top: -15px;
}
input:focus ~.inputtext2 {
	top: 0;
	z-index: 3;
	opacity: 1;
	margin-top: -15px;
}
input:focus ~.inputtext3 {
	top: 0;
	z-index: 3;
	opacity: 1;
	margin-top: -15px;
}
.btn {
	cursor: pointer;/*光标呈现为指示链接的指针（一只手）*/
	width: 250px;
	height: 40px;
    text-align: center;
    line-height: 40px;
    background: dodgerblue;
    border-radius: 5px;
    margin: 0 auto;
    margin-top: 50px;
    color: white;
    font-size: 12px;
}